Thermal head and manufacturing method thereof

Abstract

A thermal head is defined as is its manufacture, the thermal head being produced on a substrate by forming a glaze layer having a number of bubbles by printing on it a glass paste containing a glass powder that contains at least 20% by weight or more of a finely divided glass powder with an average particle diameter of up to 5 μm followed by calcining, and forming a heat generating resistor, an electrode and a protective layer successively on the glaze layer.

We claim: 
     
       1. A thermal head comprising a substrate, a glaze layer formed on said substrate, and a heat generating resistor and electrode means formed successively on said glaze layer, wherein said glaze layer is formed by printing on said substrate a glass paste of which the glass component comprises a glass powder composition of 20 to 100% by weight of a finely-divided glass powder having an average particle diameter of up to 5 μm and 0 to 80% by weight on the basis of the total amount of said glass powder composition of a glass powder having an average particle diameter of 8 to 20 μm, and by calcining said glass paste on said substrate to form a plurality of bubbles in said glaze layer. 
     
     
       2. A thermal head as claimed in claim 1, wherein said average particle diameter of said finely-divided glass powder is from 0.5 to 1.0 μm. 
     
     
       3. A thermal head as claimed in claim 1, further comprising a protective layer of silicon which contains 5 to 40% on an atomic basis of nitrogen on said heat-generating resistor and said electrode means. 
     
     
       4. A thermal head as claimed in claim 1, wherein said glaze layer is in the form of a ridge and a ridge section having a width wider than the width which would contact a heat sensitive object is formed on said substrate with a distance existing between said glaze layer and said ridge section. 
     
     
       5. A thermal head as claimed in claim 2, further comprising a protective layer of silicon which contains 5 to 40% on an atomic basis of nitrogen on said heat-generating resistor and sais electrode means. 
     
     
       6. A thermal head as claimed in claim 2, wherein said glaze layer is in the form of a ridge and a ridge section having a width wider than the width which would contact a heat sensitive object is formed on said substrate with a distance existing between said glaze layer and sid ridge section. 
     
     
       7. A method for producing a thermal head comprising a substrate, a glaze layer on said substrate, and a heat generating resistor and electrode means formed successively on said glaze layer, wherein said glaze layer is formed by printing on said substrate a glass paste of which the glass component comprises a glass powder composition of 20 to 100% by weight of a finely-divided glass powder having an average particle diameter of up to 5 μm and 0 to 80% by weight on the basis of the total amount of said glass powder composition of a glass powder having an average particle diameter of 8 to 20 μm, and by calcining said glass paste on said substrate in such a way that said glaze layer has a plurality of bubbles. 
     
     
       8. A method for producing a thermal head as claimed in claim 7, wherein said average particle diameter of said finely divided glass powder is from 0.5 to 1.0 μm. 
     
     
       9. A method for producing a thermal head as claimed in claim 7, wherein said glass paste on said substrate is calcined at a temperature that is higher than the softening point of said glass powder mixture by 50° to 150° C. 
     
     
       10. A method for producing a thermal head as claimed in claim 8, wherein said glass paste on said substrate is calcined at a temperature that is higher than the softening point of the glass powder mixture by 50° to 150° C.